1. Field of the Invention
The invention relates to a process cartridge and a recording apparatus. The process cartridge is structured from multiple removable components and contains a photosensitive drum, developing unit, and other parts that relate to the development process.
2. Description of Related Art
A conventional process cartridge of the type noted above incorporates an photosensitive drum, developing unit, charger, toner hopper, cleaning unit, waste toner box, and other components used in the image development process, in the cartridge.
The components contained in the process cartridge do not have a uniform service life. That is, some of the components have a relatively long service life, and some have a short one. In regard to the type of process cartridge that can be replenished with toner, the service life of the entire cartridge is only as long as that of the component with the shortest service life. Furthermore, as expensive and inexpensive components must all be replaced together with the installation of a new cartridge, the expense of replacing the cartridge increases the cost of operating the photocopier.
One attempt to reduce the process cartridge replacement expense has been to divide the cartridge into two sub-assemblies in which the first sub-assembly consists of the photosensitive drum, charger, cleaning unit, and waste toner box, and the second sub-assembly consists of the developing unit and toner hopper. With this type of structure, only the second sub-assembly is replaced when the toner in the hopper has been depleted. As the service life of the developing unit is generally shorter than that of the photosensitive drum, only the second sub-assembly, which includes the developing unit, is replaced when a refill is required, thus reducing the toner refill expense.
The structure discussed above, however, has some inherent shortcomings which are explained below.
A photoelectric copying process using the jumping development method generates a larger amount of waste toner than the standard development method. As a result, the service life of the first sub-assembly that contains the waste toner box can be shortened to a period of time equivalent to the service life of the second sub-assembly, thus necessitating replacement of the first sub-assembly while the photosensitive drum contained therein remains usable.
To solve this problem, it has been proposed that the waste toner box be structured as a separate component that essentially becomes a third sub-assembly. Structuring the process cartridge in this manner avoids replacing the first sub-assembly while the photosensitive drum is still usable, and thus reduces the expense of operating the photocopier.
If the process cartridge is designed to be disassembled into a greater number of separate components, however, the number of replaceable components increases as well as the frequency of component replacement. The problem with this design is that it diminishes the convenience and ease with which the process cartridge, which contains various image processing components, can be replaced.
In the process cartridge structure delineated above, the developing unit and toner hopper are contained in the second sub-assembly, so both components must be replaced concurrently despite the fact that the developing unit is a more expensive component than the toner hopper.
The present invention, when applied to a recording apparatus that may even employ the jumping development method which generates a large amount of waste toner, offers the benefits of an easy process cartridge replacement procedure and reduced replacement cost.
The present invention puts forth the following mechanisms and structures to rectify the problems discussed above.
The present invention provides a process cartridge includes a first unit and a second unit separable from the first unit. The first unit includes a photosensitive member, a developing unit that forms an image on the photosensitive member, and a cleaning unit that collects residual toner from the photosensitive member. The second unit includes a toner hopper unit that supplies toner on the photosensitive member, and a waste toner box that stores the collected residual toner. The developing unit engages with the toner hopper unit so as to engage the first unit with the second unit.